javax.servlet.http
Interface HttpSession

public abstract interface HttpSession

Provides a way to identify a user across more than one page
request or visit to a Web site and to store information about that user.

The servlet container uses this interface to create a session
between an HTTP client and an HTTP server. The session persists
for a specified time period, across more than one connection or
page request from the user. A session usually corresponds to one
user, who may visit a site many times. The server can maintain a
session in many ways such as using cookies or rewriting URLs.

This interface allows servlets to

View and manipulate information about a session, such as
the session identifier, creation time, and last accessed time

When an application stores an object in or removes an object from a
session, the session checks whether the object implements
HttpSessionBindingListener. If it does,
the servlet notifies the object that it has been bound to or unbound
from the session. Notifications are sent after the binding methods complete.
For session that are invalidated or expire, notifications are sent after
the session has been invalidatd or expired.

When container migrates a session between VMs in a distributed container
setting, all session atributes implementing the HttpSessionActivationListener
interface are notified.

A servlet should be able to handle cases in which
the client does not choose to join a session, such as when cookies are
intentionally turned off. Until the client joins the session,
isNew returns true. If the client chooses
not to join
the session, getSession will return a different session
on each request, and isNew will always return
true.

Session information is scoped only to the current web application
(ServletContext), so information stored in one context
will not be directly visible in another.

getAttribute(java.lang.String name)
Returns the object bound with the specified name in this session, or
null if no object is bound under the name.

java.util.Enumeration

getAttributeNames()
Returns an Enumeration of String objects
containing the names of all the objects bound to this session.

long

getCreationTime()
Returns the time when this session was created, measured
in milliseconds since midnight January 1, 1970 GMT.

java.lang.String

getId()
Returns a string containing the unique identifier assigned
to this session.

long

getLastAccessedTime()
Returns the last time the client sent a request associated with
this session, as the number of milliseconds since midnight
January 1, 1970 GMT, and marked by the time the container recieved the request.

int

getMaxInactiveInterval()
Returns the maximum time interval, in seconds, that
the servlet container will keep this session open between
client accesses.

setAttribute(java.lang.String name,
java.lang.Object value)
Binds an object to this session, using the name specified.

void

setMaxInactiveInterval(int interval)
Specifies the time, in seconds, between client requests before the
servlet container will invalidate this session.

Method Detail

getCreationTime

public long getCreationTime()

Returns the time when this session was created, measured
in milliseconds since midnight January 1, 1970 GMT.

Returns:

a long specifying
when this session was created,
expressed in
milliseconds since 1/1/1970 GMT

Throws:

IllegalStateException - if this method is called on an
invalidated session

getId

public java.lang.String getId()

Returns a string containing the unique identifier assigned
to this session. The identifier is assigned
by the servlet container and is implementation dependent.

Returns:

a string specifying the identifier
assigned to this session

getLastAccessedTime

public long getLastAccessedTime()

Returns the last time the client sent a request associated with
this session, as the number of milliseconds since midnight
January 1, 1970 GMT, and marked by the time the container recieved the request.

Actions that your application takes, such as getting or setting
a value associated with the session, do not affect the access
time.

Returns:

a long
representing the last time
the client sent a request associated
with this session, expressed in
milliseconds since 1/1/1970 GMT

setMaxInactiveInterval

Specifies the time, in seconds, between client requests before the
servlet container will invalidate this session. A negative time
indicates the session should never timeout.

Parameters:

interval - An integer specifying the number
of seconds

getMaxInactiveInterval

public int getMaxInactiveInterval()

Returns the maximum time interval, in seconds, that
the servlet container will keep this session open between
client accesses. After this interval, the servlet container
will invalidate the session. The maximum time interval can be set
with the setMaxInactiveInterval method.
A negative time indicates the session should never timeout.

Returns:

an integer specifying the number of
seconds this session remains open
between client requests

setAttribute

Binds an object to this session, using the name specified.
If an object of the same name is already bound to the session,
the object is replaced.

After this method executes, and if the new object
implements HttpSessionBindingListener,
the container calls
HttpSessionBindingListener.valueBound. The container then
notifies any HttpSessionAttributeListeners in the web
application.

If an object was already bound to this session of this name
that implements HttpSessionBindingListener, its
HttpSessionBindingListener.valueUnbound method is called.

If the value passed in is null, this has the same effect as calling
removeAttribute().

Parameters:

name - the name to which the object is bound;
cannot be null

value - the object to be bound

Throws:

IllegalStateException - if this method is called on an
invalidated session

IllegalStateException - if this method is called on an
invalidated session

removeAttribute

public void removeAttribute(java.lang.String name)

Removes the object bound with the specified name from
this session. If the session does not have an object
bound with the specified name, this method does nothing.

After this method executes, and if the object
implements HttpSessionBindingListener,
the container calls
HttpSessionBindingListener.valueUnbound. The container
then notifies any HttpSessionAttributeListeners in the web
application.

Parameters:

name - the name of the object to
remove from this session

Throws:

IllegalStateException - if this method is called on an
invalidated session

IllegalStateException - if this method is called on an
invalidated session

invalidate

public void invalidate()

Invalidates this session then unbinds any objects bound
to it.

Throws:

IllegalStateException - if this method is called on an
already invalidated session

isNew

public boolean isNew()

Returns true if the client does not yet know about the
session or if the client chooses not to join the session. For
example, if the server used only cookie-based sessions, and
the client had disabled the use of cookies, then a session would
be new on each request.

Returns:

true if the
server has created a session,
but the client has not yet joined

Throws:

IllegalStateException - if this method is called on an
already invalidated session